EP0788857B1 - Wire sawing device - Google Patents

Description

The present invention relates to a wire sawing device comprising a frame and a sheet of wires stretched between at least two wire guide cylinders and held in position by grooves provided on the surface of said cylinders thread guides and which define the interval between the threads of said ply which are likely to move in an alternating or continuous movement in support against a workpiece mounted on a support, each wire guide cylinder having an outer covering comprising at least two segments removable which can be fixed to the periphery of a central cylindrical part wire guide cylinders.

There are known wire sawing devices comprising so general a layer of thread capable of moving in a movement continuous or alternative pressing against a workpiece thus defining an area sawing. The sawing area consists of a set of cylinders placed in parallel. These cylinders, called wire guides, are engraved with grooves defining the interval between the wires of the tablecloth, ie the thickness of the slices. The workpiece is fixed on a support table which moves perpendicular to the layer of threads. The moving speed defines the cutting speed. The renewal of the thread as well as the control of its tension is done in a part called the wire management area outside the actual sawing area called. The agent which will govern the cutting is either an abrasive fixed on the wire, or an abrasive free brought in slip form. The wire acts only as a conveyor.

When cutting the workpiece into thin slices, the tensioned wire is both guided and towed by the wire guide cylinders. These generally coated cylinders of a layer of synthetic material are engraved with grooves whose geometry and dimensions must be very precise. The process of cutting that uses an abrasive either fixed or free, necessarily results in a wear of the material which constitutes the surface of the thread guide cylinders, therefore modifies the dimensions and the geometry of said grooves. The thread guide cylinders are usually made of a hollow or solid monobloc part coated with a synthetic element in which are engraved the grooves maintaining the spacing son of the sheet and fixed at least at one of its ends by one or more bearings containing the bearings. The wire guide cylinder is removable for ability to recondition after wear of its coating.

US Patent 4,134,384 describes such wire guide cylinders comprising a outer tubular member with polyurethane layers and one layer INVAR steel. Patent application JP 0,514,696,8 describes a type of cylinder metallic thread guide with guide grooves for the threads and a coating of synthetic material covering this thread guide cylinder.

These thread guide cylinders which constitute wear elements have a duration limited life and the grooves provided on their surface must be periodically resized by rectification, or by turning. This operation is done outside the sawing device on a cylindrical grinder or a controlled lathe digital for example. The number of re-cuts depends on the importance of each cut, the geometry of the grooves and the initial thickness of the coating. When the covering is completely used, the installation is carried out a new coating by molding, injection or any method which proves suitable for the chosen coating. When resizing is necessary, the Wire guide cylinders must be removed and removed from the sawing device. This operation is generally cumbersome due to the mechanical complexity of the wire guide cylinders and their drive system. In addition it requires outside handling assistance. We will therefore have a shutdown of the significant sawing which will decrease the overall productivity of the assembly. During the change in the thickness of the slices to be sawn, a change in the pitch of the grooves cut on the surface of the wire guides is compulsory and also requires changing the wire guide cylinders, a long and complex operation so little desirable.

Slice precision, very important for applications electronic, depends on the position of the wires during sawing as well as the supporting elements of the workpiece, therefore of the position of the wire guide cylinders compared to the workpiece, but also the quality of the geometry of the grooves cut on the surface of the wire guides. Wear of these causes a degradation of the accuracy of the slices obtained. It is clear that stopping the sawing device for reworking grooves is only necessary and therefore we tend to push it to the last end, thereby causing a decrease in the average quality of the slices as well obtained.

The document DE 2.428.111 A representing the closest state of the art, describes a wire sawing device with wire guide cylinders with two removable segments that can be attached at the periphery of a central cylindrical part of the wire guide cylinder.

This central part is mounted on one side on the machine frame and includes a free end on which a cover is fixed with a screw Central. This cover is provided with a holding part arranged so as to center and maintain the two segments forming a continuous exterior surface. If you want to replace the segments, it is necessary to remove the cover with the holding piece. Then it is possible to remove the segments by releasing them axially to an opposite holding part.

The machine according to this document therefore allows an exchange of the coating. outside by removing the holding piece at the free end of the wire guide cylinder and by axially disengaging the segments. Since the cylinders wire guides are only held at one of their ends, their parallelism is not not guaranteed due to the high forces exerted by the wires of the layer of wires. The sawed slices can therefore have geometric inaccuracies which prohibit their use for certain applications.

When holding the wire guide cylinders at both ends supported by the frame, it is no longer possible to dismantle and exchange the segments and the outer coating of the wire guide cylinders without disassembly complete with these thread guide cylinders, which is a complicated operation requiring prolonged machine shutdown.

The object of the present invention is therefore to produce a sawing device ensuring high precision of sawn slices due to the maintenance of wire guide cylinders at both ends, while allowing exchange quick and easy external coating of wire guide cylinders without having to disassemble the wire guide cylinders from the sawing frame.

The sawing device is characterized for this purpose by the fact that the segments are fixed on said central cylindrical part by fixing members arranged in recesses provided on the cylindrical outer surface of the wire guide cylinder parallel to the axis of the latter, said cylindrical part central being supported at its two ends by the frame.

A very quick and easy renewal or regeneration is thus obtained wire guide grooves and improved slice accuracy thereby that the regeneration of the surface is facilitated and uncomplicated. The changes in the pitch of the grooves by modifying the thickness of the edges are also greatly facilitated.

Thus, to avoid dismantling all of the wire guide cylinders by view of a re-machining of the grooves, we can do the operation by changing only the surface of the wire guide cylinders by providing them with a fixed removable surface mechanically, with or without bonding. The cutting of the grooves can be done in situ in the sawing device by a re-cutting mechanism which allows rework these on the surface of the wire guide cylinders without dismantling them, or before mounting the removable segments on a lathe or a grinding machine digital control for example. This allows regeneration after wear, or changing the pitch of the grooves to change the thickness slices.

This sawing technique which requires perfect groove geometry will see the accuracy of the slices increase by the fact that the regeneration of the surface is facilitated by the rapid interchangeability of the segments removable and that cutting can be done in situ or before mounting, on the removable segments.

Productivity and application precision requirements for semiconductor use, related to dimensions sawing pieces therefore slices, require that even small variations should be avoided. The use of pre-cut inserts or no, allows surface regeneration or change not easily so more frequently. In addition, she requires low additional investment since only the segments are necessary and not the whole wire guide cylinders.

The invention therefore allows the sawing device to by the concept of the interchangeability of the surface of thread guide cylinders and by the use of removable segments meet the new requirements of technology by removing a long and tedious operation which is the complete disassembly of the wire guide cylinders while improving the quality of both geometric performance than productivity. The sawing device therefore comprises wire guide cylinders with interchangeable surface advantageously in the form of removable segments held mechanically or by gluing and having their pre-cut surface with grooves or not.

Wire guide cylinders with interchangeable surface will be in the form of a basic cylinder which can receive on its surface and with an indexed position coated or uncoated segments on which the grooves used for spacing the turns of the saw wire. These grooves can be pre-cut on a external cutting with identical indexing positions to those of the wire guide cylinder, this to guarantee the position of the grooves after mounting on the device wire sawing.

The use of the concept of interchangeability the surface therefore makes it possible to produce a sawing device efficient with high productivity, precision increased average and easily changes the thickness slices produced.

Other advantages emerge from the characteristics expressed in the dependent claims and the description setting out the invention below in more detail at using drawings which represent schematically and at As an example, an embodiment and a variant.

Figure 1 is a perspective view of a mode execution of the wire sawing device.

Figure 2 is a perspective view of a cylinder guide-son.

Figure 3 shows a variant of the cylinder guide-son.

The wire sawing device of Figure 1 illustrates the principle of the present invention. The room saw 1 is pressed against the wire ply 2 supported by the wire guide cylinders 4. The support table 3 on which the workpiece 1 is fixed is moved by the engine 15. The thread guide cylinders 4 are supported at their ends by bearings 5. The removable segments 6 are mechanically fixed on the surface of the cylinders wire guide 4 by screws 7. The assembly is mounted in a frame 14. The wires of the sheet 2 are likely to be driven by known means so as to be moved according to an alternating or continuous movement. The outer surface segments 6 includes etched grooves 9 in which wire and placed. These grooves 9 define the interval between the wires of the sheet 2, so the thickness sawn slices. Since segments 6 are mechanically and / or glued to the surface of the wire guide cylinders 4, it is possible to renew them or to change them after wear or when we want to modify the distance between the grooves 9 without dismantling and put the thread guide cylinders out of the machine 4.

Figure 2 shows in perspective a cylinder wire guide 4 with fixed axis, with two removable segments 6 coated with a layer of polyurethane 8 pre-cut with grooves 9 and fixed on the wire guide cylinder 4 mechanically by fixing screws 7. The segments are positioned on the wire guide cylinder 4 by pins positioning 11. The removable segments 6 are made of metal and the latter is preferably chosen with a low coefficient expansion, for example an Fe-Ni alloy.

Figure 3 shows in perspective a variant of the wire guide cylinder 4 for attachment to cones 12. The three removable segments 6 are sheets of material synthetic, advantageously polyurethane, stretched and clamped on the surface by clamping tabs 13 mechanically fixed to the surface by screws 7. Bonding polyurethane sheet 6 associated with a texture the surface of the wire guide cylinder 4 maintains this in position on the surface of the wire guide cylinder 4.

Generally, the saw wire forming the web of wires 2 between the wire guide cylinders 4 consists spring steel with a diameter between 0.1 and 0.2 mm for sawing blocks of hard materials or compositions more specific, such as silicon, ceramic, composed of elements from groups III-V, GGG (Garnet Gadolinium-Gallium), sapphire, etc., in slices of 0.1 to 5mm about thick. The abrasive agent is a product of trade and can be diamond, silicon carbide, alumina, etc., in a form attached to the wire or in the form free in slip.

The sawing device allows by the concept of interchangeability from the surface of the wire guide cylinders 4 by adding removable segments 6, to obtain a maximum performance, productivity and flexibility, without this being to the detriment of the quality of parts produced.

It is understood that the embodiments described above are in no way limiting and that they can receive any desirable changes to inside the frame as defined by claim 1.

So other types of interchangeable surfaces can be considered which by their concept also have the regeneration and / or renewal function of the surface without disassembly of the wire guide cylinders 4. By example, the contiguous winding of a profiled rope or a strip on the surface can be considered. A reload by spraying into the sawing device by example, can also satisfy the concept of interchangeability of the surface and object of the present invention as long as it does not require complete disassembly of the wire guide cylinder 4.

Claims (7)

1. Wire sawing device comprising a frame (14) and a layer of wires (2) stretched between at least two wire guide cylinders (4) and maintained in position by grooves (9) provided on the surface of said wire guide cylinders (4) and which define the interval between the wires of said layer (2) which are adapted to be displaced with an alternating or continuous movement whilst bearing against a piece (1) to be sawed mounted on a support (3), each wire guide cylinder (4) having an external cladding (8) comprising at least two removable segments (6) adapted to be fixed on the periphery of a central cylindrical portion of the wire guide cylinders, characterised by the fact that the segments are fixed on said central cylindrical portion by means of fixing members (7,13) disposed in hollows provided on the external cylindrical surface of the wire guide cylinders (4) parallely to the axes of the latter, said central cylindrical portion being supported by the frame (14) on its two extremities.
2. Device according to claim 1, characterised by the fact that the removable segments (6) on the wire guide cylinders (4) are of metal clad with a synthetic material (8) in which the grooves (9) are incised.
3. Device according to claim 2, characterised by the fact that the synthetic material is polyurethane.
4. Device according to claim 2, characterised by the fact that said metal is selected from metals with low coefficient of thermal expansion.
5. Device according to claim 1, characterised by the fact that the fixing members are constituted by screws (7) placed in the hollows located on the opposing extremities of the segments.
6. Device according to claim 1, characterised by the fact that the guide cylinders (4) comprise positioning pins (11) ensuring the positioning of the removable segments (6) on the central cylindrical portion.
7. Device according to claim 1, characterised by the fact that the removable segments (6) are constituted by sheets of synthetic material fixed and/or cemented on the surface of the central cylindrical portion, the fixing members being constituted by securement strips (13) fixed by screws (7) on the central cylindrical portion in longitudinal hollows of the external surface of the wire guide cylinders.

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